Cloudiness problem with my aquarium

Question
Hi Matt,

I sure hope you can help! I have had a cloudiness problem since I set up my 55 gallon tank up 3 months ago. i bought 2 oscars (african cichlids) about i inch long and 2 plecostomus about the same size. I'm using a filter that I bought at wallmart for 45 to 65 gallon tanks i have cleaned the filter a numerous amount of times and have changed the water about 6 times and to no luck i even changed the rocks and gravel because i noticed some were lime stones/ coral rocks and they were dissolving in the water and causing it to become cloudy, The pet store told me it could be the ph level being low but that was not the problem either,after 2 or 3 days you can see the cloudiness again, I have had these same type of fish in the same size tank and very similar filter size and I have had fish my entire life and never have i encountered this problem.
Please help Thanx Gus, Miami, FL  

Answer
Hi Gus,
Cloudiness normally happens because a tank has crashed.  Some tanks crash by removing an old filter and adding a new one because the mass amount of beneficial bacteria that are harbored in the old are completely removed whereas the new one has nothing.  Beneficial bacteria is essential for breaking down toxins.  Thus, the tank cannot break down the toxins fast enough because such a large portion of it was removed from the old filter.  The tank goes into bacterial bloom to try to adjust to the new situation, causing a cloudiness.
Another reason why some tanks crash is by adding a large amount of fish at a time.  The bioload goes from small to large instantly with no time for the tank to adapt to the increasing bioload.  Here, the tank also goes into bacterial bloom to try to adjust to the new situation, causing the same cloudiness.

Try to think of a reason why your tank crashed.  When you "cleaned" your filter, did you use tap water?  Tap water kills the beneficial bacteria which is why it is suggested that you clean a filter inside a bucket of used aquarium water that was taken out during a water change.  Did you add a bunch of any new fish?  Did you replace an old filter with a new one?  In order to add a new filter, you must run both the old and new at the same time so the new can start growing bacteria, whereas the old one can continue its job until the new filter is cycled.  

Majority of the cloudiness is from tank crashing.  Try to think back at what could possibly happened to make your tank crash.  Cloudy water usually goes away over time after a tank has adjusted itself.  You dont need to do many water changes.  The only time you need to do the water changes is if the toxin levels are high.  Ammonia and Nitrite should never be higher than 1ppm.  It should actually be 0ppm in a cycled tank.. if it is not 0ppm then it means your tank is under a minicyle or is still not cycled.  The Nitrate should never be more than 40ppm.  Liquid testing can measure these 3 toxins.  Liquid testing only.  Test strips are worthless and are too inaccurate to use.  

Also, low ph does not cause cloudiness.  If that was the case.. rainwater,well water, reverse osmosis water, and water sold in water bottles would be cloudy because the pH is 6.0 whereas tap water in cities are 7.6.  The majority of the employees jobs at the fish stores are not very knowledgeable and are only there for selling.
-Matt-